Results of an early access treatment protocol of daratumumab in United States patients with relapsed or refractory multiple myeloma

Background: Daratumumab is a human CD38-directed monoclonal antibody indicated for the treatment of relapsed and refractory multiple myeloma (MM). Methods: A multicenter, open-label treatment protocol provided early access to daratumumab for patients who had progressive MM after they received ≥3 prior lines of therapy that included a proteasome inhibitor and an immunomodulatory agent or if they were refractory to both a proteasome inhibitor and an immunomodulatory agent. Patients received daratumumab 16 mg/kg weekly for 8 weeks, every other week for 16 weeks, and monthly until they developed disease progression, unacceptable toxicity, or 60 days after the drug gained US approval. Treatment-emergent grade ≥3 adverse events (AEs), serious AEs, and AEs of special interest were collected. Results: Three hundred forty-eight patients were enrolled at 39 US sites between June and December 2015. Patients received study therapy for a median of 1.9 months (range, 0.03-6.0 months). Fifty-two percent of patients transitioned to commercially-available daratumumab and 37% discontinued because of progressive disease. Grade ≥3 AEs occurred in 50% of patients, including thrombocytopenia (15%) and anemia (14%). Serious AEs occurred in 35% of patients (12% were drug-related), including infections (11%). Infusion reactions occurred in 56%, 2%, and 2% of patients during the first, second, and all subsequent infusions, respectively; respiratory symptoms (cough, dyspnea, throat irritation, nasal congestion) were common. The infusion reaction rate for the first infusion was 38% in 50 patients at 2 sites who received montelukast as premedication for their first infusion and 59% in patients who did not receive montelukast. Conclusions: The current findings are consistent with previously reported trials and confirm the safety profile of daratumumab in heavily pretreated US patients who have relapsed or refractory MM. Cancer 2018;124:000-000.